JP2536089B2 - Optical disc master exposure method - Google Patents

Description

The present invention relates to an optical disc master exposure method, and more particularly to an optical disc master exposure method for an optical disc for inter-groove recording.

[Conventional technology]

Generally, as the exposure power of the exposure using the optical disc master exposure method, as shown in FIG.
Address pit 2 provided between the groove 1 and the groove
There is known a pattern for recording between grooves, which is composed of The exposure of such an optical disk master requires two laser beams capable of power control and modulation in order to expose the tracking V groove 1 and the address pit 2.

Two laser beams separated by a laser beam interval of 1/2 of the track pitch P are focused and focused on the photoresist disc by a known autofocus method, and further, the photoresist disc is rotated to rotate the photoresist disc one by one. Spiral exposure can be performed by moving the track pitch P and exposing the power-controlled laser beam on the photoresist disk from the circumference to the circumference.

The address pits 2 are exposed by ON-OFF modulating the laser beam for address pit exposure, and the tracking V groove exposure beam is continuously exposed from the inner circumference to the outer circumference, and the tracking V groove 1 is exposed. Perform exposure.

FIG. 4 is a cross-sectional view after the exposure processing of the address pits 2 and the tracking V groove 1 on the photoresist disk using the conventional optical disk master exposure method and the development processing.

Since the beam intensity distribution is a Gaussian distribution, the two laser beams overlap each other.

Therefore, although there is a degree of difference depending on the exposure power of the two laser beams, the distance between the two laser beams, etc., film loss d due to fogging occurs at the parts on both sides of the address pit, as shown in FIG. It tends to have a pit cross-sectional shape.

[Problems to be Solved by the Invention]

However, in the above-described conventional optical disc master exposure method described above, the tracking V groove and the address pits are simultaneously exposed by the two laser beams, so that 2
Since the laser beams of this book partially overlap each other, film loss occurs on both sides of the pit, the cross-sectional shape of the address pit does not become rectangular, and the cross-sectional shape of the address pit fluctuates from the design value due to minute fluctuations in exposure conditions. As a result, there is a drawback that the electrical characteristics obtained from the address pits are deteriorated in the optical disc medium obtained by transferring the produced optical disc master.

This is because the track pitch P is, for example, 1.4 in order to increase the density.
If it is made as small as μm, it becomes a bigger problem.

[Means for solving the problem]

The optical disc master exposure method of the present invention reduces the exposure power of the beam for tracking V-groove exposure that is simultaneously exposed when the address pits are exposed, and performs exposure by using the tracking V-groove in a portion without pits. Configured to be shallow.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

1 (a) and 1 (b) are timing charts showing an embodiment of the present invention, and FIG. 1 (a) is a power control of a tracking groove exposure power PW1 of a laser beam for tracking V groove exposure. As an example, FIG. 1B shows an example of power control of the address pit exposure power PW2 of the laser beam for address pit exposure.

The optical disk master exposure method shown in FIG. 1 reduces the exposure power of the laser beam for tracking V-groove exposure to 75% of the normal level when exposing the address pits, and the laser beam for tracking V-groove exposure and the address pits. It is possible to prevent the film loss from occurring on both side portions of the address pit due to the overlap with the exposure laser beam.

FIG. 2 shows an address pit 2 and a tracking V groove 1 on a photoresist disk according to the embodiment shown in FIG.
FIG. 3 is a cross-sectional view after performing the exposure and development processing. The cross-sectional shape of the address pit 2 is a shape close to a rectangular design value without film reduction. Further, even if a slight change in the exposure power such as the exposure power of the two laser beams and the interval between the two laser beams occurs, the change in the sectional shape of the address pit 2 can be suppressed. As a result, it is possible to prevent deterioration of the electrical characteristics obtained from the address pits 2 in the optical disc medium obtained by transferring the produced optical disc master.

In the above-described embodiment, the exposure power of the beam for V-groove exposure for tracking is reduced to 75% of the normal level, but the exposure power may be lowered to the minimum exposure power that can form a V-groove for tracking.

〔The invention's effect〕

The optical disk master exposure method of the present invention reduces the exposure power of the beam for tracking V groove exposure during address pit exposure to make it shallower than the tracking V groove in the pitless portion, thereby forming a film on both side portions of the pit. Since it is possible to prevent the decrease, it is possible to make the cross-sectional shape of the address pits closer to the rectangular shape of the design value, and it is possible to form the address pits stably even if there is a slight change in the exposure condition. In the optical disc medium obtained by transferring from the optical disc master, the electrical characteristics obtained from the address pits can be stabilized.

[Brief description of drawings]

1 (a) and 1 (b) are timing charts showing an embodiment of the present invention, FIG. 2 is a sectional view of a pattern shape exposed by the embodiment shown in FIG. 1, and FIG. FIG. 4 is a plan view showing an example of an exposure pattern exposed by a conventional optical disc master exposure method, and FIG. 4 is a sectional view of a pattern shape exposed by using the conventional example. 1 ... V groove for tracking, 2 ... Address pit PW1 ... V groove exposure power for tracking, PW2 ...
Address pit exposure power, P ... Track pitch,
P '... Laser beam spacing, d ... Film loss.

Claims (1)

(57) [Claims] 1. An optical disk master is exposed with address pits for recording track numbers and sector numbers with a first laser beam for address pit exposure, and the first laser beam and the track pitch are halved. The tracking V-grooves are exposed by a second laser beam which is arranged in parallel at an interval of, and has an exposure power which is smaller than the exposure power at the time of exposure at the portion without the address pits when the address pits are exposed. A method for exposing an optical disc master, which comprises: